Windows: STOP: C0000221 unknown hard error

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Posted on March 17, 2009

STOP: 0xC0000221 unknown hard error
C:\Winnt\System32\Ntdll.dll (or another specific file or driver)

* This error does not mean what it say.. use the matrix to decode the message**

My solutions was to replace the memory module as it had a bad crc checksum . this will not allow the windows installation to continue. After replacing the memory module the error cleared.

I have also found that some users were able to clear the error by change the ultra dma mode for their harddrive to 5 instead of 6. another option was to disable this mode all together.

In summary this is most likely a hardware issue with the harddrive , memory , or cdrom drive.

Good luck and I hope this helps someone.
M$ Reference